Heretofore, in order to prevent an electrical short circuit (liquid junction) between an electrical activation unit of a fuel cell stack and an external low electrical resistance member (such as a metal member) via generated water, which is generated in the fuel cell stack, there has been considered countermeasures for electrical short circuit in a fuel cell stack, in particular, in a gas outlet region thereof including respective members around a reaction gas outlet. For example, there is known a fuel cell system in which a discharge pipe connected to a reaction gas discharge through hole of a fuel cell stack, is formed with an electrically insulating member (for example, refer to Patent Document 1).
However, according to this fuel cell system, if the discharge pipe is formed long and insulation resistance is increased, the strength of the discharge pipe may be reduced in some cases, and there is a problem in that the arrangement of the discharge pipe becomes complex and the size of the piping structure becomes large.
In response to this type of problem, there has conventionally been known a fuel cell stack in which, for example, the tip end of an outlet pipe connected to a fuel gas discharge through hole of the fuel cell stack is accommodated in the interior thereof, and there is provided a water collection tank for accumulating generated water discharged from the tip end of this outlet pipe (for example, refer to Patent Document 2).
This fuel cell stack is of a configuration such that the highest water level of generated water, which drips from the tip end of the outlet pipe and which is accumulated in the water collection tank, is distanced vertically downward from the tip end of the outlet pipe by just a predetermined distance, and thereby, conductive paths, which may be formed by generated water, are blocked.